AbstractThe degree of transport and retention of ¹⁴CH₄ in soil is being investigated in a series of laboratory experiments in preparation for field scale trials at the University of Nottingham. The experimental programme focusses on the behaviour and fate of ¹⁴CH₄ injected into subsoil and its subsequent incorporation into vegetation under field conditions. Due to restrictions on the use of radioactive tracers in the field, ¹³CH₄ is being used as a surrogate gas which can be handled conveniently in the laboratory and field and which can be measured with high precision using gas chromatography with isotope ratio mass spectrometry. The laboratory data indicate significant differences between the diffusion and oxidation rates of ¹³CH₄ in re-packed and undisturbed soil columns, with both rates appearing to be significantly lower in undisturbed soils. Data from both laboratory and field experiments will be used to inform the development of a model of ¹⁴CH₄ migration and its fate in the biosphere above a geological disposal facility.